Differentiation analysis of VOCs in Kunming during rainy and dry seasons based on monitoring high temporal resolution

Abstract

Volatile Organic Compounds (VOCs) play a pivotal role as precursors for O3 formation. 66 VOCs species in Kunming were observed for two consecutive years using an online monitoring system. Concentration characteristics of VOCs, ozone formation potential (OFP), sources and health risks in rainy and dry seasons were investigated. Our results showed that the concentrations of VOCs exhibited significant seasonal differences, with average concentrations of 31.43 ± 17.62 μg/m3 and 64.78 ± 36.38 μg/m3 in the rainy and dry seasons, respectively. Alkanes (16.83 ± 16.75 μg/m3) dominated the VOCs types throughout the monitoring period, followed by halogenated hydrocarbons (13.38 ± 16.20 μg/m3), olefins (10.77 ± 14.34 μg/m3), aromatics (6.64 ± 6.71 μg/m3), and alkynes (0.36 ± 0.37 μg/m3). The OFP values in rainy and dry seasons were 86.10 μg/m3 and 198.55 μg/m3, respectively. The most substantial contribution to OFP originated from olefins, which could be associated with crude oil refining activities around Kunming. Vehicles and petrochemicals were the main sources in Kunming based on PMF calculations. Biomass burning (10.63%) and biogenic emission (8.68%) were noted in dry and rainy seasons, respectively. HYSPLIT analysis established that Kunming's air quality was significantly affected by the southwestward air mass transmission, particularly through a large industrial park. In the dry season, Kunming is significantly more affected by air mass transport from this direction than in the rainy season. The carcinogenic risk of benzene was high as 10 × 10−6 and 2.4 × 10−6 in the rainy and dry seasons, respectively. In conclusion, Kunming's VOCs control measures should pay more attention to the influence of the upwind industrial park.